The present invention relates to a drip irrigation system and also to a method of drip irrigation. The invention also relates to a control unit particularly useful in the drip irrigation system and method.
Drip irrigation is now widely used in water irrigation systems, wherein a water supply conduit is connected to a plurality of dripper tubes each provided with a plurality of emitter openings along its length for discharging water at a slow rate from each opening. Such dripper tubes are thus capable of supplying water directly to the region of the plants at a very slow rate, thereby saving water and frequently also increasing yields.
At the present time, such dripper tubes are operated at flow rates of at least one or two liters per hour at each emitter opening. If the dripper tubes are operated at lower flow rates in the existing systems, there would be little if any discharge from the emitter openings at the ends of the dripper tubes particularly in long lines and/or in irregular land topography. Drip irrigation systems also commonly use pressure-compensated emitters for purposes of equalizing as much as possible the discharge rates of the emitters along the length of the tube irrespective of the length of the tube and/or the topography on which the dripper tube is used. However, even in pressure-compensated drippers, there is still a minimum discharge rate, of the order of one or two liters per hour, which must be provided if the dripper tube is to operate satisfactorily along its complete length.
An object of the present invention is to provide a water irrigation system which enables dripper tubes to be operated at substantially lower discharge rates than heretofore possible and still provide satisfactory performance of the dripper tube along its complete length. Another object of the invention is to provide a method of irrigation using dripper tubes of various constructions, including those presently used as well as those that may be used in the future, but which permit the dripper tubes to be satisfactorily operated at substantially lower discharge rates than heretofore possible for the complete length of the dripper tube. A further object of the invention is to provide a novel control unit which may be introduced into existing drip irrigation systems to provide the foregoing advantages.
According to one aspect of the present invention, there is provided a water irrigation system, comprising: a water supply conduit; a dripper tube having a plurality of water discharge openings along its length for discharging water at a slow rate from each opening; and a pulsator device connecting the the water supply conduit to the dripper tube and producing a pulsatile water flow to the dripper tube having a frequency substantially exceeding one cycle per second (CPS).
Preferably, the pulsator device produces a pulsatile water flow to the dripper tube having a frequency exceeding 10 CPS. Particularly good results are obtainable when the pulsator device is connected to the dripper tube by a connecting tube of a length and cross-sectional area such as to produce a resonant feedback system with the pulsator device producing a pulsatile water flow to the dripper tube having a frequency exceeding 10 CPS.
I have found that a water irrigation system constructed in accordance with the foregoing features enables dripper tubes designed to produce a discharge rate of about one or two liters per hours per emitter opening, may be operated in accordance with the present invention to output the water at a fraction of that rate, e.g., at about 0.2-0.5 liters per hour, and still enable all the emitter units along the length of the dripper tube to output the water at this extremely low rate. While the particular mechanism of action involved in this result is not known with certainty, it is believed that the pulsator device, particularly when used with the connecting tube as described above, produces, by resonance feedback, a pulsatile flow of such a high frequency and intensity as to more effectively distribute or xe2x80x9cpumpxe2x80x9d the water along the complete length of the dripper tube even during low-flow conditions. Such high-frequency pulsations are believed to overcome the resistance of the water flow even with such low flow rates as would, in conventional dripper tube systems, fail to produce water discharge at the far ends of the dripper tubes.
The expression xe2x80x9cpulsatile water flowxe2x80x9d is used herein in its broadest sense, to include not only an interrupted water flow, wherein the pulsations are distinct pulses separated by interruptions in the water flow (as in a conventional pulsator system), but also a continuous water flow wherein the pulsations are modulations or ripples in the continuous water flow. Actually, the latter would be the preferred case in most applications of the invention wherein a resonant feedback is utilized to produce the high frequency pulsations exceeding 10 CPS.
Such a system is capable of producing very sizeable water savings without sacrificing crop yields. In some cases, the crop yields may be even increased despite the relatively small amount of water used.
In addition, an additional water supply may be coupled to an inlet to the dripper tube just downstream of the control valve, thereby permitting pressurized water in the water supply conduit to actuate the pulsatile device to act as a pump for pumping the water inletted to the dripper tube from the additional water supply. The additional water supply may be, for example, a water container collecting waste water from other sources, such as from air conditioning systems, collected rainwater, etc.
According to another aspect of the present invention, there is provided a water irrigation system, comprising: a water supply conduit; a dripper tube provided with a plurality of emitter openings along its length for discharging water at a slow rate from each emitter opening; a control valve connecting the water supply conduit to the dripper tube; and a pulsator device connecting the water supply conduit from a point upstream of the control valve to the dripper tube at a point downstream of the control valve; the control valve having an open position to produce a continuous water flow from the water supply conduit to the dripper tube to fill the dripper tube; and a closed position to produce a pulsatile water flow from the water supply conduit to the dripper tube via the pulsator device.
According to a further aspect of the present invention, there is provided a control unit for use in a drip irrigation system having a water supply conduit and a dripper tube provided with a plurality of emitter openings along its length for discharging water at a slow rate from each emitter opening; the control unit comprising: a housing having an inlet end connectable to the water supply conduit, and an outlet end connectable to the dripper tube; a valve member within the housing movable from an open position for permitting water flow from the inlet to the outlet, and to a closed position for blocking water flow from the inlet to the outlet; a pulsator device having an inlet connected to the housing between its inlet and the valve member; and a connecting tube connected between the outlet of the pulsator device and the housing between its outlet and the valve member.
Such a control unit could thus be connected into an existing drip irrigation system, between the water supply conduit and each dripper tube, to enable such a system to be operated at much lower discharge rates than their original design rates, or those considered to be heretofore possible in existing drip irrigation systems, to provide substantial water savings as well as possible increases in crop yields.
According to yet another aspect of the present invention, there is provided a method of irrigation, comprising: supplying water from a water supply conduit to a dripper tube provided with a plurality of emitter openings along the length of the dripper tube; and feeding the water from the water supply conduit to the dripper tube via a pulsator device which produces a pulsatile water flow to the dripper tube at a frequency substantially exceeding 1 CPS. Preferably, in accordance with the described preferred embodiments, the pulsator device is connected to the dripper tube by a connecting tube of a length and cross-sectional area such as to produce a resonant feedback system with the pulsator device producing a pulsatile water flow to the dripper tube having a frequency exceeding 10 CPS.
According to a still further aspect of the invention, there is provided a method of irrigation, comprising: supplying water from a water supply conduit to a dripper tube provided with a plurality of emitter openings along the length of the dripper tube; initially feeding the water from the water supply conduit to the dripper tube at a high rate to at least partially fill the dripper tube with water and to start to produce discharges of water from the emitter openings at a relatively low rate from each emitter opening; and thereafter feeding the water from the water supply conduit to the dripper tube at a low rate via a pulsator which produces a high-frequency pulsatile water flow within the dripper tube effectively moving the water along the length of the dripper tube to the emitter openings. For example, and as indicated earlier, the pressurized water supply conduit could be used as a source of pressure for causing the pulsatile device to act as a pump for pumping water collected from other sources, such as from air conditioning systems, rainfall, etc., thereby enabling a further savings of water to be effected.